diff --git a/index.bs b/index.bs
index f39d69e4..f12fa92b 100644
--- a/index.bs
+++ b/index.bs
@@ -12264,8 +12264,8 @@ in which case they are exposed on every object that [=implements=] the interface
         <emu-val>undefined</emu-val>; there is no [=attribute setter=] function.
     1.  Assert: |attribute|'s type is not a [=promise type=].
     1.  Let |steps| be the following series of steps:
-        1.  If no arguments were passed, then [=JavaScript/throw=] a <l spec=ecmascript>{{TypeError}}</l>.
-        1.  Let |V| be the value of the first argument passed.
+        1.  Let |V| be <emu-val>undefined</emu-val>.
+        1.  If any arguments were passed, then set |V| to the value of the first argument passed.
         1.  Let |id| be |attribute|'s [=identifier=].
         1.  Let |idlObject| be null.
         1.  If |attribute| is a [=regular attribute=]: